JPH03154418A - State variable circuit - Google Patents

Abstract

PURPOSE:To set a cut-off angular frequency and sharpness independently by forming a sum current and a difference current formed based on two reference current sources, giving the sum current to one of two integration devices and giving the difference current to the other. CONSTITUTION:A sum current and a difference current formed based on two reference current sources 5, 6 are formed, the sum current is given to one of two integration devices 1, 2 and the difference current is given to the other. When a variable current source 5 is varied to change a current I0, only a cut-off angular frequency omega0 is varied while the sharpness Q is almost made constant and when a variable current source 6 is varied to vary a current IQ, only the sharpness Q is varied while keeping the cut-off angular frequency omega0 almost constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a state variable circuit used to equalize a reproduced waveform, for example in a digital audio tape recorder.

[Summary of the invention]

This invention consists of two integrators, and by controlling the current values given to the two integrators and varying the time constants of the two integrators, the cutoff frequency and sharpness Q can be adjusted. In a state variable circuit that can set two reference current sources, a sum current and a difference current of the two reference current sources are formed, and the sum current is given to one of the two integrators to integrate one of them. The cutoff frequency and sharpness Q can be set independently by setting the time constant of the integrator, applying a difference current to the other of the two integrators, and setting the time constant of the other integrator. It has been made possible.

[Conventional technology]

For example, in a digital audio tape recorder,
A state variable filter whose basic circuit is a Gilbert type integrator is used to equalize the reproduced waveform reproduced from the rotary head. A state variable filter using this Gilbert type integrator as a basic circuit will be explained.

For example, based on the Gilbert type multiplier described in Japanese Patent Publication No. 48-20932, as shown in FIG.
A Gilbert-type integrator is constructed.

In FIG. 4, a resistor 103 is connected between the emitter of the transistor 101 and the emitter of the transistor 102, and the emitter of the transistor 101 is connected to the collector of a transistor 104 as a current source.
The emitter of transistor 102 is connected to the collector of transistor 105 as a current source. transistor 1
A non-inverting input terminal 106 is derived from the base of 01.

An inverting input terminal 107 is led out from the base of transistor 102 . The emitter of transistor 104 is connected to ground terminal 100. The emitter of transistor 105 is connected to ground terminal 100.

The collector of transistor 101 is connected to the emitter of transistor 108 and to the base of transistor i13. The collector of transistor 102 is connected to the emitter of transistor 109, and
Connected to the base of transistor 112.

Collector of transistor 108 and transistor 109
The collector of is connected to the power supply terminal 111. The base of transistor 10B and the base of transistor 109 are connected to voltage source 110.

The emitter of transistor 112 and the emitter of transistor 113 are commonly connected, and this connection point is connected to the collector of transistor 114 as a current source. The emitter of transistor 114 is connected to ground terminal 100.

The collector of transistor 112 is connected to the connection point between the collector of transistor 115 and its base. The collector of transistor 113 is connected to the collector of transistor 116, and also connected to the base of transistor 117 and one end of capacitor 118.

The base of transistor 115 and the base of transistor 116 are commonly connected. The emitter of the transistor 115 and the emitter of the transistor 116 are connected to the power supply terminal 111.
connected to.

A voltage source 119 is connected between the other end of the capacitor 11B and the ground terminal 100. The emitter of transistor 117 is connected to ground terminal 100 via current source 120, and output terminal 121 is led out from the emitter of transistor 117.

A collector of transistor 117 is connected to power supply terminal 111.

The bases of transistors 104 and 105 are commonly connected, and this connection point is connected to the base of transistor 122 and its collector. The emitter of transistor 122 is connected to ground terminal 100. A collector of transistor 122 is connected to power supply terminal 111 via resistor 123.

Transistor 1140 base is connected to the base of transistor 124 and its collector. transistor 12
The emitter of 4 is grounded. The collector of the transistor 124 is externally connected to one end of a resistor 125. The other end of the external resistor 125 is connected to the power supply terminal 111.

Signals supplied to input terminals 106 and 107 are voltage-to-current converted by a ■-■ conversion circuit consisting of transistors 101 and 102, and then supplied to a Gilbert-type multiplier consisting of transistors 112 and 113, transistors 108 and 109, and transistor 114. be done. A capacitor 118 is provided on the output side of this Gilbert multiplier.

The output of this Gilbert type multiplier is taken out from an output terminal 121 via an emitter follower transistor 117.

The transfer characteristic of the Gilbert type multiplier as shown in Fig. 4 is
Let the signal voltages from input terminals 106 and 107 be v, and v
t, the output voltage is V. , when the voltage of the voltage source 119 is Vc, the following equation is obtained. Here, Vc =.

Then, S This is the characteristic of the integrator.

The time constant ω× of this circuit is the transistor 04 and 10
The current value of the current source consisting of 5 is IA, and the current value of the transistor 14 is
When the current value of the current source consisting of is 6, the resistance value of the resistor 103 is R, the capacitance of the capacitor 118 is C, and the emitter resistance of the transistors 01 and 102 is r, it can be expressed as 8 IA.

As shown in equation 0, in such a Gilbert type integrator, the time constant ω8 is determined by the ratio of the current value IA of the current source made up of the transistors 104 and 105 and the current value Ill of the current source made up of the transistor 114.

Since the transistors 104 and 105 as current sources and the transistor 122 constitute a current mirror circuit, the current value 1 is set by the resistor 123. Since the transistor 14 and the transistor 24 as current sources constitute a current mirror circuit, the current value is 1.
is set by an external resistor 125.

The resistance value of resistor 123 is R11, and the resistance value of resistor 125 is R
18, and since rIIoc-ocRll °T'■ m, it becomes Ro.

Since the resistor 103 and the resistor 123 are arranged within the integrated circuit, the ratio of the resistance value R11 of the resistor 123 to the resistance value R of the resistor 103 is constant. Therefore, . As can be seen from equation (2), the time constant ω8 can be set by varying the resistance value R1t of the external resistor 125. Such a Gilbert-type integrator is not affected by variations in resistance within the integrated circuit.

The above-mentioned Gilbert type integrator will be represented by a block as shown in FIG.

A state variable filter can be constructed using such a Gilbert type integrator. That is, in FIG. 6, a resistor 161 is connected between the input terminal 151 and the inverting input terminal of the Gilbert type integrator 141. The input terminal 152 and the non-inverting input terminal of the Gilbert type integrator 14 are connected.

A resistor 162 is connected between the inverting input terminal of Gilbert-type integrator 141 and its output terminal. A resistor 163 is connected between the inverting input terminal of Gilbert-type integrator 141 and the output terminal of Gilbert-type integrator 142. An output terminal 155 is led out from the output terminal of the Gilbert type integrator 141, and a resistor 16 is connected between the output terminal of the Gilbert type integrator 141 and the non-inverting input terminal of the Gilbert type integrator 142.
4 is connected.

Non-inverting input terminal of Gilbert type integrator 142 and input terminal 1
A resistor 165 is connected between the resistor 54 and the resistor 165.

Inverting input terminal of Gilbert type integrator 142 and input terminal 15
3, a resistor 166 is connected between the two. A resistor 1 is connected between the inverting input terminal of the Gilbert type integrator 142 and its output terminal.
67 is connected. An output terminal 156 is led out from the output end of Gilbert type integrator 142 .

In the circuit configured as shown in FIG. 6, input signals can be applied from input terminals 151 and 152, 153 and 154, and output signals can be taken out from output terminals 155 and 156.

Filters with various characteristics can be realized depending on the resistance values of the resistors 161 to 167. That is, the transfer characteristics of such a circuit are as follows: (1): Input signal voltage v2 from input terminal 151 : Input signal voltage v from input terminal 152 : Reference voltage v4 connected to Gilbert type product divider 1 : Output signal voltage v from the output terminal 155, : Input signal voltage v from the input terminal 153, : Input signal voltage v from the input terminal 154, : Reference voltage connected to the Gilbert type product divider 2, : Output Output signal voltage from terminal 156, 3. , resistor, 6. Resistance A □ e: Resistance value of resistor 162 3/8 resistance 163 (7) resistance A.

e m: resistance value of resistor 164 0 :Resistance 16 5 resistance value 0 :Resistance value of resistor 166 0 :Resistance value of resistor 167 however, a+b+c÷1 f+g=1 a+e-1 C≠0 Then, it is shown as follows.

(Left below) Also, the cutoff frequency ω of this filter. and sharpness Q
Ha, ω. Army J” bg+cd ω, ω, ...■.

In Equation 0, a=b=e=f-O y 3w y , w O , the configuration of a low-pass filter as shown in FIG. 7 is obtained. The transfer characteristic of this low-pass filter is ωO-fω^ω1...■Q-IMK7stoneτ...■.

As shown in the above equation, when such a filter is configured, the cutoff angular frequency ω can be adjusted by varying the current values 11 and I2 given to the Gilbert multipliers 141 and 142. and sharpness Q can be set.

FIG. 8 is an example of a conventional state variable filter. 8th
As shown in the figure, conventionally, variable current sources 171 and 172 are provided, and the cutoff angular frequency ω and sharpness Q can be set by varying the currents (Il!II and I2). .

FIG. 9 shows a circuit for setting the currents I and I2. In FIG. 9, the emitter of transistor 183 is connected to ground terminal 182. The collector and base of transistor 183 are connected to power supply terminal 181 via variable resistor 185. Along with this, transistor 1
830 base is connected to transistor 1840 base. The emitter of transistor 184 is connected to ground terminal 182. A current output terminal 186 having a current value II is led out from the collector of the transistor 184.

The emitter of transistor 193 is connected to ground terminal I82. The collector and base of transistor 193 are connected to power supply terminal 181 via variable resistor 195. At the same time, the base of transistor 193 is connected to the base of transistor 194. transistor 19
The emitter of No. 4 is connected to the ground terminal 182. A current output terminal 196 with a current value of 2 is led out from the collector of the transistor 194.

Variable resistor 185 sets the current flowing through transistor 183. A current mirror circuit is constructed from transistors 183 and 184.

Therefore, by varying the variable resistor 185, the current value 11 obtained from the current output terminal 186 can be varied.

Further, the current flowing through the transistor 193 is set by the variable resistor 195. Transistors 193 and 194
A current mirror circuit is constructed. Therefore, by varying the variable resistor 195, the current output terminal 19
The current value 1□ obtained from 6 can be varied.

[Problem to be solved by the invention]

However, as shown in FIG.
1 and 172 are provided separately to set the current values I and I.
2, the cutoff angular frequency ω. A problem arises in that it is difficult to set the sharpness Q and the sharpness Q independently.

That is, the time constants ω and ω of the Gilbert-type integrators 141 and 142 are the current values 11 and I! given to the integrators 141 and 142, respectively. Set by. Cutoff angular frequency ω. depends on the product of current values 11 and 12,
The sharpness Q is determined according to the ratio between the current values 1 and 12.

Therefore, when one of the current values 11 and I2 is moved, the cutoff angular frequency ω. and sharpness Q move at the same time.

In particular, as shown in FIG. A variable current source 202 is provided which generates a current I3. In such a configuration, the cutoff angular frequency ω. The adjustment of the sharpness Q and the sharpness Q becomes very complicated, and three variable current sources are required.

Therefore, it is an object of this invention to obtain the cutoff angular frequency ω
. The object of the present invention is to provide a state variable circuit in which the sharpness Q and the sharpness Q can be set independently.

[Means to solve the problem]

This invention consists of two integrators whose time constants are set by controlling the current value, and state variables in which the cutoff frequency and sharpness Q can be set according to the time constants of each of the two integrators. In the circuit, two reference current sources 5.6 which can be controlled independently of each other are provided, and two reference current sources 5.6 are provided.
．． A sum current and a difference current of the currents formed based on 6 are formed, the sum current is given to one of the two integrators 1 and 2, and the sum current is given to the other of the two integrators 1 and 2. This is a state variable circuit designed to provide a differential current.

[Effect]

The current value I is set by varying the variable current source 5. When changing the cutoff angular frequency ω while keeping the sharpness Q almost constant. only can be changed. Also, by varying the variable current 'rA6, the current value 1. When changing the cutoff angular frequency ω. It is possible to vary only the sharpness Q while keeping it almost constant.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. 1st
In the figure, 1 and 2 are Gilbert type integrators. An input terminal 3 is connected to a non-inverting input terminal of the Gilbert type integrator l. The output terminal of Gilbert type integrator 1 is connected to the non-inverting input terminal of Gilbert type integrator 2. The output terminal of the Gilbert type integrator 2 is connected to the output terminal 4, and also connected to the inverting input terminal of the Gilbert type integrator 2 and the inverting input terminal of the Gilbert type integrator 10.

The variable current source 5 and the variable current source 6 have a cutoff angular frequency ω of this filter. and a current source for setting the sharpness Q. As will be explained later, the cutoff angular frequency ω is adjusted by varying the variable current a5 and the variable current source 6. and sharpness Q can be set substantially independently.

Variable current source 5 is connected to current sources 7 and 8 in a current mirror manner. The variable current source 6 is connected in a current mirror with currents a9 and 10. Current I set by variable current source 5. A current equal to is passed through the current source 7, and a current 3■ which is three times the current I0 set by the variable current source 5. is the current source 8
be swept away by

The current setting is set by the variable current source 6. A current equal to is applied to the current sources 9 and 10.

The voltage aIo set by the current source 7 and the current ■ set by the current source 9. The sum current (IO+IQ) is the current addition circuit 1.
1, and this sum current (io+■.) is supplied to the Gilbert type integrator 1 as a current 11 that determines the time constant ω4 of the Gilbert type integrator 1. A difference current (3101Q) between the current 3L set by the current source 8 and the current I0 set by the current source 10 is formed in the current addition circuit 12, and this difference current (31°-Io) is generated by the Gilbert type integrator 20. It is supplied to the Gilbert type integrator 2 as a current I2 that determines the time constant ω.

When Gilbert type integrators 1 and 2 are connected as shown in FIG. 1, a second-order low-pass filter can be constructed. The cutoff angular frequency ω of this low-pass filter. and the sharpness Q are as shown in the above equations 0 and 0, It is determined by a constant.

The time constants ω and ω of Gilbert type integrators l and 2 are as follows:
Since it is set by the current values I and I2 given from the current adding circuits 11 and 12, respectively, ωo = l ωa(J)lccJ I + 'I
z ”'■Q-7 stone T7τ1 工f ding 7 Got... @.

Gilbert type integrators 1 and 2 are given currents 11 and I2 from current adders 11 and 12, and this current 11
and I2 is 1,=1°+1. ...[Phase] Iz=31o 1a...■.

From formula 0 and formula 0, the current value I. When increasing, the current value ■
1 and I2 both become large. When current value I0 is decreased, both current values I and I2 are decreased. In other words, the current value ■. When changing the current value 1. and I2
both change in the same direction, and both time constants ω1 and ω change in the same direction. By changing the current value I0, the current (Ii
! When both I + and I2 are changed in the same direction, the cutoff angular frequency ω is obtained from equation 0. changes greatly.

At this time, the ratio between the time constants ω1 and ω does not change much, so from equation 0, the sharpness Q hardly changes.

On the other hand, if the current value I0 is increased, the current value ■,
However, the current value I2 becomes smaller. Current value I9
When I decrease, the current value 11 decreases, but the current value I
2 becomes larger. That is, when the current value I0 is changed, the current values 11 and (2) change in opposite directions. When the current value ■9 is changed and the time constants ω and ω□ are changed in opposite directions, the cutoff angular frequency ω is changed from ■2. remains almost unchanged. At this time, the time constant ω.

Since the ratio between .

Therefore, in one embodiment of the invention, the variable current 'a5
When the current value I0 is changed by varying the cutoff angular frequency ω while keeping the sharpness Q almost constant. only can be changed.

Furthermore, when the variable current source 6 is varied to change the current value r, the cutoff angular frequency ω. It is possible to vary only the sharpness Q while keeping it almost constant. That is, in one embodiment of the present invention, the cutoff angular frequency ω.

and sharpness Q can be set independently.

Furthermore, as shown in Fig. 2, before the secondary filter,
When a third-order filter is configured by disposing a Gilbert type integrator 15, a current source 16 constituting a current mirror circuit with the variable current source 5 is disposed, and the current of this current source 16 is passed through the Gilbert type integrator 11. , the Gilbert type integrator 15
The configuration may be such that a time constant ω5 of ω5 is set. In this case, by varying the variable current source 5, the current value
By changing the cutoff angular frequency ω while keeping the sharpness Q almost constant. only can be changed. In addition, by varying the variable current source 6, the current value I0
By varying the cutoff angular frequency ω. It is possible to vary only the sharpness Q while keeping it almost constant.

FIG. 3 shows a specific configuration of a current setting circuit for setting the current value I0 and the 10% current values 11 and 2 in the filter shown in FIG. In Figure 3, transistor 2
The second emitter is connected to the power supply terminal 21. The collector of the transistor 22 is connected to the ground terminal 20 via the variable resistor 23.
Both are connected to 2. The collector of transistor 22 and its base are commonly connected, and this connection point is connected to the base of transistor 240 and the base of transistor 250. The emitter of transistor 25 is connected to power supply terminal 21 .

The emitter of transistor 24 is connected to power supply terminal 21 . The collector of transistor 24 is connected to the collector of transistor 26 and its base. transistor 2
6 emitters are connected to ground terminal 20. The collector of transistor 26 and its base are connected to the base of transistor 27. The emitter of transistor 27 is connected to ground terminal 20.

The emitter of transistor 28 is connected to power supply terminal 21 . The collector of the transistor 28 is connected to the ground terminal 20 via the variable resistor 30, and the transistor 28
8 and their bases are commonly connected, and this connection point connects the base of transistor 31 and transistors 32 to 8.
Connected to the base of 34.

The emitter of transistor 31 is connected to power supply terminal 21 . The collector of transistor 31 and the collector of transistor 25 are commonly connected, and this connection point is connected to the collector of transistor 35 and its base. The emitter of transistor 35 is connected to ground terminal 20. The base of transistor 35 is connected to the base of transistor 36. The emitter of the transistor 36 is connected to the ground terminal 20
connected to. A current value of 1. A current output terminal 37 is led out.

Transistors 32 - 34 are connected in parallel, and the emitters of transistors 32 - 34 are connected to power supply terminal 21 . The collectors of transistors 32 to 34 and the collector of transistor 27 are commonly connected, and this connection point is connected to the collector of transistor 38 and its base. The emitter of transistor 38 is connected to ground terminal 20. The base of transistor 38 is connected to the base of transistor 39. The emitter of the transistor 39 is the ground terminal 20
connected to. A current output terminal 40 having a current value I2 is derived from the collector of the transistor 39.

A current value I0 is set by the variable resistor 23, and this current value 1a is passed through the transistor 22.

Since the transistor 22 and the transistor 24 constitute a current mirror circuit, this current value I. A current equal to I is caused to flow through transistor 24, and this current is caused to flow through transistor 26, which is arranged in series with i-transistor 24. Since the transistor 26 and the transistor 27 constitute a current mirror circuit, the transistor 27
The current value I. A current equal to is applied. Also, since the transistor 22 and the transistor 25 constitute a current mirror circuit, this current value is ■. A current equal to is caused to flow through the transistor 25.

The current value I is determined by the variable resistor 30. is set, and this current value I0 is passed through the transistor 28.

Since the transistor 28 and the transistor 31 constitute a current mirror circuit, this current value ■. A current equal to is passed through the transistor 31.

Furthermore, since the transistor 28 and the transistors 32 to 34 constitute a current mirror circuit, this current value I
A current equal to 0 is passed through the transistors 32 to 34, and the connection point of the collectors of the transistors 32 to 34 has a current of
A current of 31o is applied.

The collector of transistor 25 and the collector of transistor 31 are connected to each other. The transistor 25 has ■. A current of Io is caused to flow through the transistor 31. Therefore, in the transistor 35,
A current of (10+IQ) is applied. transistor 3
5 and the transistor 36 constitute a current mirror circuit, so the transistor 35 has (10+xo)
When a current of (Io+1
, ) is applied. Therefore, a current of (Io +Io) can be obtained from the current output terminal 37. This current is assumed to be 11.

Collectors of transistors 32 to 34 and transistor 2
This connection point is connected to the collector of transistor 38. Transistors 32-34
For parallel connection, 31. A current of Io is caused to flow through the transistor 27. Therefore, a current of (31o 1.) is caused to flow through the transistor 38. Since a current mirror circuit is constituted by transistor 38 and transistor 39, transistor 3
When a current equal to (31o Io) is passed through the transistor 39, a current equal to (31o 1o) is passed through the transistor 39. Therefore, from the current output terminal 40, (3
A current of 1o 1a ) can be obtained. This current is assumed to be 12.

〔Effect of the invention〕

According to this invention, when the variable current source 5 is varied to change the current value I0, the cutoff angular frequency ω is maintained while the sharpness Q is kept almost constant. only can be changed. In addition, the variable current source 6 is varied to obtain the current value I.

When changing the cutoff angular frequency ω. It is possible to vary only the sharpness Q while keeping it almost constant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of another embodiment of the invention, FIG. 3 is a connection diagram of an example of a current forming circuit in an embodiment of the invention, and FIG. Figure 4 is a connection diagram used to explain the Gilbert type integrator, Figure 5 is a block diagram used to explain the Gilbert type integrator, Figure 6 is a block diagram used to explain the state transition filter, and Figure 7 is the Gilbert type integrator. 8 is a block diagram used to explain a conventional state transition filter, and FIG. 9 is a connection diagram of an example of a current forming circuit in a conventional state transition filter. , FIG. 10 is a block diagram used to explain another example of the conventional B-shaped transition filter. Explanation of main symbols in the drawings 1.2, 15: Gilbert type integrator 5: input terminal, 4: output terminal. 6: Variable current source. 8.9, 10: Current source 1.12: Current addition means.

Claims (1)

[Claims] In a state variable circuit that is composed of two integrators whose time constants are set by controlling the current value, and in which the cutoff frequency and sharpness Q can be set according to the time constants of each of the two integrators, Can be controlled independently of each other2
two reference current sources are provided, a sum current and a difference current of the currents formed based on the two reference current sources are provided, one of the two integrators is given the sum current, and one of the two integrators is provided with the sum current; A state variable circuit in which the difference current is given to the other of the two integrators.